1. Field of the Invention
The present invention relates to an image recording apparatus, and more particularly to an image recording apparatus that discharges ink from multiple nozzles onto a recording medium to record an image, wherein the ink is prevented from bleeding.
2. Description of the Related Art
Conventionally, one known example of an image forming apparatus is an inkjet recording apparatus (inkjet printer) that has an inkjet head (ink discharge head) with an alignment of multiple nozzles and that forms an image on a recording medium by discharging ink from the nozzles while moving the inkjet head and the recording medium relative to each other.
Various methods are known in conventional practice as ink discharge methods for such an inkjet recording apparatus. Known examples include a piezoelectric system wherein a vibration plate that constitutes part of a pressure chamber (ink chamber) is deformed by the deformation of a piezoelectric element (piezoelectric ceramics), the capacity of the pressure chamber is changed, ink is led into the pressure chamber from an ink supply channel during this increase in pressure chamber capacity, and the ink in the pressure chamber is discharged as droplets during the decrease in pressure chamber capacity. Further, known examples also include a thermal inkjet system wherein ink is heated to create air bubbles for discharging the ink by the expansion energy when the air bubbles grow.
In image recording apparatuses that have ink discharge heads such as an inkjet recording apparatus, ink is supplied from an ink-storing tank to ink discharge heads via an ink supply channel, and the ink is discharged by the various discharge methods described above, but depending on the type of ink or the type of recording medium, the ink dots (ink droplets) may bleed after striking the recording medium, or the dot shapes may break up and cause the image to fade. When a color image is recorded using a plurality of inks with different colors, if an image is recorded by overlapping ink of a different color on previously recorded ink that has not yet dried, then problems are encountered with the colors bleeding or mixing together and adversely affecting the image quality.
In view of this, various methods have been proposed in conventional practice for improving the image quality by preventing the image from fading due to the ink bleeding, or preventing the colors from bleeding or mixing together when an image is recorded by overlapping inks of different colors.
In one known example, during one rotation of the rotating body that holds the recording medium, the ink dots of various colors sprayed from the recording heads of various colors are recorded on the recording medium by pixel skipping in a state of separation by at least one dot in the sub-scanning direction, which is the same as the rotational direction, thus preventing adjacent ink dots from mixing or flowing together and recording a high-quality image (for example, see Japanese Patent Application Publication No. 2000-71481).
In another known example, an inkjet recording apparatus has a device for estimating the dried state of the recorded ink, and the velocity at which the recording medium is conveyed is varied and the intervals between recording heads are varied according to the results of this estimation, whereby the recording interval between one recording and the next is varied to maintain the throughput of the recording apparatus, which prevents recording discrepancies in sections where different inks overlap and improves the image quality (for example, see Japanese Patent Application Publication No. 03-247450).
In another known example, in a color inkjet recording method, a color print free of smearing between colors is obtained by performing a routine in which printing by at least one of a plurality of heads is performed after a time that is sufficiently longer than the print lag time of adjacent heads is allowed to pass before printing is performed by the other heads in the same printed area (for example, see Japanese Patent Application Publication No. 04-173250).
However, for example, the example described in Japanese Patent Application Publication No. 2000-71481 is disadvantageous in that during one rotation of the rotating body that holds the recording medium, an image is recorded with single-dot pixel skipping, a plurality of rotations are needed to record an entire image, and the productivity is reduced.
Also, the example described in Japanese Patent Application Publication No. 03-247450 has a device for estimating drying and a device for adjusting the dot recording intervals. The device is designed to adjust the intervals at which the next dots are recorded according to the dried state, but this example does not have a fixing device for drying and hardening the ink that strikes the recording medium and relies merely on natural drying. The device is disadvantageous in that mixed color fading and image bleeding cannot necessarily be reliably prevented.
Furthermore, the example described in Japanese Patent Application Publication No. 04-173250 merely uses a time greater than the print lag between adjacent dots, does not have a device for drying and hardening, and is subject to the same problems as Japanese Patent Application Publication No. 03-247450.